A. Field of the Invention
The present invention relates to foam sports boards for recreational use, and more particularly to bodyboards or snow sleds having a thermoformed skin laminated to a foam core.
B. Discussion of Related Art
Body boards for riding waves and other recreational sports boards made of foam or other floatation material are known in the prior art. In general, such boards are made of a number of polyethylene foam and polyethylene film layers that are laminated together by heating the layers and then immediately passing them through a pair of nip rollers. The heating process causes adhesion by the localized collapse and bonding of the foam cells on the surface of the respective layers. Another conventional process of lamination is to apply heat to the film layer with a heated nip roller on the film side and a normal nip roller on the foam side, where the heated nip roller may be a flat roller. In most cases the surface of the heated nip roller contains an engraved pattern of convex and concave areas for better heat transfer. The resulting laminate of the polyethylene foam and polyethylene film is then often heat laminated onto a standard foam core.
Because the standard foam core does not have a perfectly flat or planar surface, adhesive contact between the film and foam core is limited to the apexes of the cells on the surface of the foam core. The point of contact is not uniform between the film and foam, but instead the film contacts the points of the outer surface of the core that protrude from the irregular cellular surface of the foam core.
Conventional film lamination methods typically use micro-cellular high density foam sheets to improve adhesion between the film and the foam core. The micro-cellular foam sheet contains smaller peaks and valleys with the peaks closer together. The surface area of contact between the sheet and foam is thereby increased. However, this kind of structure is still prone to delamination by mechanical contact forces and by the effects of heat and pressure when in use.
While it is known in the prior art that a thin layer of thermal plastic polyethylene film between a polyethylene foam sheet and a polyethylene film can be used to promote lamination, such thin layer of film is generally an unmodified low density polyethylene with limited efficacy. U.S. Pat. No. 5,647,784 to Moran, the disclosure of which is incorporated herein by reference, describes an intermediate bonding film layer between a polypropylene foam core and at least one upper or lower skin layer, which has a different chemical composition from the foam core material. Preferably, the intermediate layer is a terpolymer based on polyethylene vinylacetate and in the form of a thin, slit-film bonding adhesive. In the thermolamination process, the film melts and acts as glue between the different materials of the composite bodyboard.
U.S. Pat. No. 5,275,860 to D'Luzansky, et al., the disclosure of which is incorporated herein by reference, shows bodyboards and the like where the board comprises a closed cell foam core of polypropylene, a lower and upper skin of polyethylene and an intermediate layer heat bonded to the upper and lower skin. With the presence of an intermediate copolymer layer which is a mixture of 65% polypropylene and 35% polyethylene, the peel strength between the foam core and each of upper and lower skin is improved. Multi-layered bodyboards and methods of manufacture are well known in the art and one of such boards is described in application Ser. No. 10/797,995 filed on Mar. 11, 2004 and is incorporated herein by reference.
Bodyboards made by molding are well known in the art. The preferred embodiment comprises one or more channels shaped into the bottom of the board. Each channel may extend from the front to the back of the board. The top of the board may be contoured so that a person can comfortable place the upper torso portion of their body on the board. The board may further comprise a raised ridge along the front and side edges of the board to allow a rider to grasp the board. An example of a molded bodyboard is shown in the patent application US2006/0281377 to Blumenfeld, the disclosure of which is incorporated herein by reference.
Accordingly, there is need for adhesively bonded bodyboards with improved bonding between layers of different polymeric material having different surface contouring and cellular structure.